With recent advances in medical technology, increased emphasis has been placed on medical equipment and techniques that can be used and performed by patients on an outpatient or home care basis. As an example, some infusion therapy programs can now be administered at home by a patient or by medical personnel having a minimum of training.
Some infusion therapy is accomplished using an IV administration set. Such an administration set typically includes a patient interface device such as a hypodermic needle which is inserted at a venous access site on the patient. The hypodermic needle is connected to a flexible supply tube which in turn, is connected to a supply of the medical solution. The medical solution may be dispensed by gravity from a bag suspended from a pole or by an infusion device such as a peristaltic or volumetric pump coupled to a supply of the medical solution.
Recently, elastomeric infusion devices have been utilized for dispensing medical solutions. Such elastomeric infusion devices are simpler in construction and more adaptable to home use than peristaltic pumps. An elastomeric infusion device typically includes a supply of the medical solution which is pressurized by an elastomeric membrane. In use, the medical solution is forced by the elastomeric membrane through the supply tube and into the patient. Preferably, the delivery pressure is relatively constant over the range of delivery. Such devices may be portable and disposable and in general are adaptable to use on either an inpatient or outpatient states.
As an example, a disposable elastomeric infusion system is marketed by IMED corporation, San Diego, Calif. assignee of the present application under the trademark ReadyMed 100/200.
The use of such elastomeric infusion devices, as well as use of other types of IV administration sets, requires that the supply tube be purged of air or "primed" prior to initiation of fluid flow through the supply tube and into the patient. This is because the supply tube prior to activation of the infusion device contains a dead space volume of air. A priming procedure for purging the supply tube of this volume of air must typically be performed prior to connection of the supply tube to the patient interface device (i.e. hypodermic needle) of the IV administration set.
Initially, the proximal end of the supply tube is attached to the supply reservoir of the elastomeric infusion device. The distal end of the supply tube is initially closed off using a tube clamp. For priming the supply tube, the tube clamp is adjusted, opening the supply tube and initiating fluid flow from the supply reservoir of the elastomeric infusion device and through the supply tube. This forces the dead volume of air initially contained in the supply tube out the distal end of the supply tube. When fluid reaches the distal end of the supply tube, the air in the supply tube has been purged. The supply tube is then closed off by adjusting the tube clamp and the distal end of the supply tube is attached to the patient interface device.
This procedure may be difficult to perform and time consuming for a patient or relatively unskilled medical personnel. Moreover, if the priming procedure is not performed correctly it may cause the elastomeric infusion device to function improperly. In addition, incorrect application of the procedure may have serious medical consequences for the patient, such as the introduction of excessive air and other contaminants into the vein.
Another consideration with the use of such an elastomeric infusion device is in the need to provide a constant or predictable fluid delivery pressure regardless of the quantity of solution remaining in the infusion device. In addition, the delivery pressure of the solution exiting the infusion device may be substantially higher than a desired pressure at the patient interface (i.e. hypodermic needle) and accordingly must be reduced. As an example, it is desirable to deliver most medical solutions to the patient at a pressure that is slightly greater than the mean venous pressure of the patient.
In light of the above, there is a need in the art for a tubing set that can be used with an elastomeric infusion device to provide a constant fluid delivery pressure without the need for priming the supply tube from the infusion device. Accordingly it is an object of the present invention to provide a tubing set for an infusion device for infusing medical solutions that provides a relatively constant pressure drop at constant flow and that is self priming. It is a further object of the present invention to provide a tubing set having a filter element that removes air and particles from the medical solution to be infused. It is another object of the present invention to provide a tubing set for use with an infusion device in which a minimal dead space volume is provided between the filter element of the tubing set and a patient interface device such as a hypodermic needle at a venous access site of a patient. It is yet another object of the present invention to provide a tubing set that can be calibrated for reducing the pressure from an elastomeric infusion device to just above the venous pressure of the patient. It is a further object of the present invention to provide a tubing set that is easy to use, simple in construction, and relatively inexpensive to manufacture.